US3195410A - Reproducing apparatus - Google Patents

Description

July 20, 1965 R. B. coL'rEN ETAL 3,195,410

REPRODUCING APPARATUS July 20, 1965 n.13. com-EN ETAI.

REPRODUCING APPARATUS Original Filed Sept. 2, 1959 11 Sheets-Shes t 2 /l /l/ [lig .i f, i www/MU maag.. M @m/M Man? di A H .l MMM/MW W vJuly 20, 1965 R. B. coLTEN E TAL 3,195,410

REPIgoDUcING APPARATUS A Original Filed Sept. 2, y1959 11 Sheets-Sheet 3 ATTORNEY July 20, 1965 R. B. com-EN ETAL 3,195,410

REPRQDUCING APPARATUS Original Filed Sept. 2, 1959 11 Sheets-Sheet 4 W53 ,4W [-1 1 fw irl V4 VE $59145 l wa/fm? i- Pa/w um f IN VE N TOR S ff W @my :zi @0xff/fz,

July 20, 1965 R. B. COLTEN ETAI- REPRODUGING APPARATUS Original Filed Sept. 2, 1959 11 Sheets-Sheet 5 July 20, 1965 R. B. COLTEN ETALl RPRODUCING APPARATUS Original Filed Sept. 2, 1959 l1 Sheets-Sheet 6 1 NORA/EY July 20, 1965 R. B. coLTEN ETAL 3,195,410

REPRODUCING APPARATUS original med sept. 2, 1959 11 sheetssnee17 IN VEN TORS' A TTORJVEY July 20; 1,965 R.,a=.coL1fEN ETAL 351953,410

REPRODUCING APPARATUS' Original Filed. Sept.` 2:, 1959V .11, sheetysheet 8g IN VEN TORS' A TTR/VEY `uly 20, 1965 Original Filed Sept. 2, 1959 R. a. coLTEN ETAL. 3,195,410

nEPnonucINe APrARATus 11 Sheets-Sheet 9 July 20v 1965 R. B. coL'rEN ETAL 3,195,410

REPRODUCING APPARTUS Original Filed Sept. 2, 1959 11 Sheets-Sheet 10 RA/EY July v20, 1965 R. lB. CQLTEN E1-A1,. 3,195,410

original Filed sept. 2, 1959 `11 sheets-sheez 11 ,W J-z W j?, wlw/a7( /Wff f f /f A NUR/VE? United States Patent O 3,195,410 REPRODUCING APPARATUS Robert B. Cohen, Santa Ear-hara, Calif., Glenn Wanttaja, Hales Corners, Wis., and August F. Scarpelli,

Warren, Mich., assignors to General Motors Corporation, Detroit, Mich., a corporation of Uelaware Original application Sept. 2, 1959, Ser. No. 337,607, now

Patent No. 3,105,907, dated Oct. 1, 1963. Divided and this application Oct. 12, 1961, Ser. No. 144,791

5 Claims. (Cl. 90-13) This invention relates to improvements in reproducing apparatus adapted, although not exclusively, for machining reproductions of contours from a pattern on a workpiece.

This is a division of the co-pending application Serial No. 837,607 filed September 2, 1959 and entitled Reproducing Apparatus, now Patent No. 3,165,907.

In general, since reproducing apparatus must function rapidly and accurately, automatic operation is preferred, manual operation being slow and inaccurate, even though the operator has `a high degree of skill. But for automatically operating reproducing apparatus to be effective, i.e., versatile and adaptable for different applications, it must be capable of accomplishing without complexity at least as many operations as can be achieved with manual apparatus. For example, automatically operating reproducing apparatus should desirably be capable of copying lines from a drawing or a blueprint as distinguished from expensively formed master drafts, be capable of following irregular contours without the copying tool leading or lagging the tracer mechanism so as to induce errors into the final result, be uniniuenced by lines intersecting those to be Copied, be capable of being placed on-course quickly and any extreme off-course errors should not be permitted to destroy the workpiece, and be stable and instantaneously responsive and devoid of influence from speed fluctuations.

With the foregoing in mind, the invention contemplates an automatically operating reproducing apparatus that is capable of copying irregular contours rapidly and accurately, that has unique arrangement for copying a selccted one of a series of intersecting lines, that provides novel modes both of getting on-course quickly and of stopping the apparatus when off-course, that has provision for removing speed iluctuations and inducing stability into the system, and for instantly responding with constant speed operation, that is particularly suited for copying from any type master draft, that accommodates different size workpicces so mounted as to inhibit the influence of vibrations, eg., copying tool chatten and that may be adjusted for different size cutting tools.

Because it is desirable to copy from almost any type master draft such as blueprints, photostats, etc., a tracer mechanism for the automatic reproducing apparatus often utilizes some form of radiant energy to produce information pulses, eg., photocells may be employed to sense olf-course errors and develop corresponding error signals. The photocells when used in pairs frequently, `although identical, have different outputs at times when the outputs thereof should be balanced to indicate no off-course error. Moreover, when the photocells are balanced for one condition of lighting and reflectivity, they are often out of balance when these conditions change. The outputs from `these photocells must be picked up in such a manner as to be free of noise and these signals must afford both corrections for parallel misalignments and lateral displacements relative to the contour being traced. The development of these error signals as well as some provision for causing the copying tool to be maneuvered in accordance therewith, also present problems.

Accordingly, the invention provides the reproducing Fice apparatus with a unique tracer mechanism that incorporates photosensitive means for detecting both parallel misalignments and lateral deviations thereof with respect to a contour to be traced, that has an unusual system for resolving these signals and causing an equivalent signal to be developed for controlling movement of the copying tool, that eliminates noises during pickup of the error signals, and that has a novel mode of Calibrating the photosensitive means for different lighting conditions and master drafts of different degrees of reiiectivity.

Although automatic control is desired, the apparatus should be capable of manual control at certain times, eg., provision should be made for preparing the apparatus manually for automatic operation without any excessive loss in time. With both manual and automatic controls available, then both must be coordinated so as to insure against the possibility of one system leading or lagging the other such that a workpiece could be ruined. Also, in pursuing a certain contour, it may become necessary to maintain a selected course despite the tendency for the automatic control to demand otherwise.

Therefore, the invention incorporates both manual and automatic controls so coordinated as to be synchronized and permit either automatic or manual control at any time without concern for any lost motion due to leading or lagging between the two controls. Also by the invention, under critical operating conditions as when crossing intersecting lines, the existing course can be maintained without the intersecting line influencing the operation.

When the reproducing apparatus is of considerable size, or when it is necessary to position the controls such that the operation of the copying tool relative to the Workpiece is diilicult to observe by the operator, or when personal safety prevents close observation of the apparatus, it becomes diticult to view the relative movements between the copying tool and the workpiece.

For this reason, the invention provides an operator control station, remotely positioned from the apparatus, with an unusual system for visually observing the performance of the copying tool.

ln promoting accuracy of the iinished contour, chips removed during machining operation can produce interference as well as obscure the cutting action if a substantial amount of metal is being removed. To overcome this problem, the invention affords a mode of quickly withdrawing removed chips from the cutting area. Speciiically, the invention employs a vacuum pressure system for removing the chips from the proximity of the cutting tool and the workpiece through the spindle of the cutting tool.

Generally, reproducing apparatus employs a table or the equivalent of a size adequate to accommodate the largest master draft for which the apparatus is designed. Necessarily, the draft table will be of a relatively large size, and therefore, when small drafts as well as small drawings are to be traced, it is advantageous if the small drawing can be positioned anywhere on the draft table. This permits several such small drawings to be simultaneously attached to the draft table so that the interruption of one tracing operation for another does not require interchanging of the drafts. For this feature to be possible, the apparatus usually in some way must be adjusted for the change of position of the draft on the table. To do this requires major adjustments between the tracer mechanism and the copying tool and involves expensive and complex structures.

`The invention, therefore, contemplates apparatus of the preceding character that is suited for copying master drafts attached to any part of a draft table. More particularly, the invention affords an adjustable workpiece support that permits the workpiece to be positioned on any part thereof so as to correspond to the disposition URE 11; and

of the master draft on the draft table. Additionally, by the' arrangement, the disposition of the tool support rela- ,tive to the workpiece aiords' further support kfor the workpiece. Y d i The foregoing and other objects and advantages of the invention will be apparent from the following description and the accompanying` drawings in which:`

FIGURE'l is a perspective view ofra reproducing apparatus demonstrating the principles of the invention;

FIGURE 2 is a diagram of a pressure uid system for the apparatus;

FIGURE 3 is a diagrammatic illustration ofthe apparatus optical system;

FIGURE 4 is a vieWof the reproducing operation as observed on a IV viewer;

FIGURES 4a, 4b, 4c, and 4d are diagrammatic showi tors 54Y and 6d. are operated by iluid pressure delivered .thereto under Vthe, control of horizontal and vertical uid pressure control units 66 and 568. By utilizing iluid presings illustrating different operating phases of a tracer lmechanism for the apparatus; f'

FIGURESS, 6, 7 and 8 are diagrams 'of circuits employed by the tracer mechanism;

FIGURES 9 and 9a are block diagrams of the appara- Y tus control system;

FIGURE l is a view partly schematic of a chipV removal system for the apparatus;

FIGURES 1l and l2 are frontand Vside views, respectively, of a workpiece support employed by the apparatus;

sure` operated ymotors, response is instantaneous and the iiuid has an inherent ability to absorb drive line shocks such that together smooth responsive operation is obtained.

ABoth of the fluidpressur'e control units 66 and 68 are of the character employing force motors and servo valves,

that for the horizontal drive train 50, will be somewhat briefly described. As demonstrated in FIGURE 2, a servo valve, designated generally `at 70Y and formed kwith a series of spaced lands 72, 74, A 76 and 78, is slidably positionedwithin a bore in a valve body 80. Centering FIGURES 13 and 13a are sectional views of the workpiece support taken along line l13-13 of FIGUREtll;

FIGURE l4'is a sectional view of the workpiece support taken along line 14-14 of FIGURE 11;

support looking in the direction of UREV 14; f Y

FIGURE 16 is a sectional view of a double clamp for the workpiece support:VV taken 4along line` 16--716of FIG- arrows 15-15 in FIG- FIGURE 17 is a view ofthe double clamp looking in the direction of arrows 17-17 in FIGURE 16.

GENERAL ARRANGEMENT Referring to FIGURE 1 rin detail, the reproducing apparatus depicted has horizontal guideways suitably supported on a base (not shown) orV the equivalent. A table A12 isv adapted to slide along the horizontal guideways 10 and has formed integral therewith',.or iXedly 30 FIGURE is Va view of -a clamp'for the workpiece.

y springs 82 and 84 act on opposite endsV of the servo valve 70 and maintain the servo valve 70 in the depicted center positionl'i'n the absence Vof any force except the springV bias.Y When in this' center position, lands 72 and 74 and lands 76 and 78 respectively interrupt Vcommunication between restricted eXhaust ports 86 and 88 and motorin- :lets 9@ and 92. Each of the exhaust ports 86 and 88 is `slightly restricted so as to improve operational responsiveness. -With both of the exhaust ports 86 and 88 cut oi or out of communication with kthe motor inlets 90 and 92, iluid pressure in a main supply line 94 delivered thereto by an appropriate pump 96 at apressure determined by ing therefor is deenergized. The function and purpose of positioned thereon, an upright stand 14; The rupright Ystand 14 cooperates with the table 12 to maintain vertical guid'eways 16l properly aligned soV as to permit vertical i up and downrmovement of a tool support 18 slidably joined to the vertical guideways 16. The tool supportlS has mounted thereon a tool drive motor 20 that through a `belt 22 revolves a spindle 24 to which'a copying or Y cutting tool 26 is secured adjacent a workpiece or template 28. An adjustable support for the workpiece 28 Other modes yof drivingthe ing the servo valve 70 is under the control of a force ticular applications. Also. the versatility ofthe apparatus n is increased if provision is made for revolving the copying tool at different speeds within some select range.V n' y To maneuver the cutting tool 26 relative to the workpiece 28, two Vsimilar drive trains are employed, one a horizontal drive train denoted generally at 50 and the othera vertical drive train denoted generally at 50 and the other a vertical drive train shown at 52. The .horizontal drive train 50 includes a drive' motor 54, a gear.

box 56 and a drive screw 58, Whereas the verticaldrive drive screwl 64.y Drive in each train proceedsl from the `train 52 consists of a drive motor 66, a gear box 62, and a drive screw. .Each gearbox is appropriately arranged to provide the required drive direction change at a desired drive ratio, which may be altered if wantedi From theV drivescrews 58 and 64 the rotation thereof is transferredy in any suitable way, eg., stationary nuts (not shown) atthis valve 98will become apparent. With thisA arrangement, when the servo .valve 70 is in 'the center position, the drive motor 54'isvineffective, but

when the servo valve 70 is maneuveredin either direction,

Vthe pressure supply to'one of the' motor inlets 90 lor 92 willbe reduced Vor, entirely cut off with the result that the pressure being delivered to one or the'other of the motor inlets Quand 92 willdominate and the motor 54 will be rotated thereby in the correspondingdirection. The inlet to the motorV 54 with the reduced orV cutv oi pressure will be relieved through one or the other of the'exhaust ports 86 and 88.; l

VThe production of the variable pressures for maneuvermotor *denoted generally at 100. For this control Vthe motor 160 employs a reed valve 102 pivoted at 104 and rarranged so yas to enter the valve body as viewed.

The point of entry of the yreed valve 102 into the' valve body S0 may be sealed by a seal element 106 or may be left 'openrif drainage to ,sump is possible' Energization of one or the other of oppositerelays 108 and 110 respectively by regulating signal voltages respectively from an X-axisV summing circuit 112 and an X-aXis servo ainplirier 114-and a Y-aXis summing circuit116 and a Y-aXis servo amplifier Y118 will cause the reed valve 102 to pivot 'about the axis determined by the pivot point'104 and in so doing the end entering the valve body 8i) will restrict one or the other of adjacent control orifices 128 and 122 thereby altering the pressure of the iluid acting on theopposite orifices 125 and 12d create a pressure differential between the branch 124 and the chambers at opposite ends of the servo valve 7d. Without these orifices 12d and 128, control would not be possible since uid pressure would be relieved via an exhaust chamber 130 through either of the control orifices 120 and 122 or both.

If the reed valve 1F52 is in the illustrated center position, the fluid pressure acting on opposite ends of the servo valve 70 will be relieved through the exhaust chamber 13d. However, if the reed valve 102 abuts or partially restricts one of the control orifices, eg., control orifice 120 the pressure upstream thereof will build up. This pressure, when adequate, will move the servo valve 70 to the right reducing or cutting off the supply of fluid pressure to the motor inlet 99 while increasing the supply of fluid pressure to the opposite motor inlet 92. Accordingly, the horizontal drive motor Se will revolve in a corresponding direction. Meanwhile, the motor inlet 9) will be partially or completely relieved through exhaust port 86. The same events will occur in reverse if the reed valve lf2/2 restricts control oriiice 122, i.e., the servo valve '7d now will be moved to the left so that the pressure to the motor inlet 90 will dominate while that in the motor inlet 92 is partially or completely relieved via exhaust port 3%. With this latter situation, the horizontal drive motor 5d will reverse in direction of rotation.

0n the side of the apparatus opposite the workpiece 23, a master draft table 132 is pivotally joined to sorne fixture such as the apparatus base and has attached thereto a m-aster draft 134, which may he a print, drawing, or the equivalent having a contour line as line 136 to be traced. The pivotal movement of the mas-ter draft table 132 permits the table to be positioned in a horizontal plane when the master draft 134 is attached. Then the table 132 may be moved to the demonstrated vertical position and locked in place. A number of lamps 13S are positioned in the vicinity of the master draft 134 so as to light up the part of the contour line 136 to be traced. These lamps 138 may be secured to the table 132 and/or arranged for movement with the tool support ld. Additional lamps may be employed as needed.

An optical system denoted generally `at 14) and displayed schematically in FIGURE 3, is so arranged as to provide dual images of the portion (enclosed by a circle 141) of the contour line 136 being traced. This is effected by splitting the image in a known way transferred from a lens 142 to a split image lens 14d. One of the images is transferred through an upright tower 146 (FIGURE 1) carried by the tool support 13 and projected at a magniication determined by magnifying lens 14d and 15) on a frosted glass screen 152 at the top of the tower 146. The other image proceeds through an openin 7 154 at the base of the tower 14o and is correlated with a reticle 135 simulating the copying tool 26 and an image producer as TV camera 158. Both the reticle 156 and the TV camera S are accurately positioned on a shelf 16) secured to the tool support 1S, so that an electronic image is developed thereby showing the outline of the reticle 155 superimposed on the contour line image. This enables an accurate reproduction of the disposition of the tool 26 relative to the contour line 136 being copied to be obtained, e..g., as Viewed in FIGURE 4, and is accomplished in a well-known manner by coordinating the focal lengths of the TV camera 153 and the split image lens ldd.

The image projected onto the frosted screen 152 is utilized by `a tracer mechanism denoted generally at 162 for the `automatic aspect of the apparatus, whereas the image to the TV camera 15S is through a suitable closed system projected onto the screen of a TV viewer 164 remotely positioned from the apparatus at an operators station as control panel 166 containing various manually operated controls. This permits the operators station to be in a room different from the apparatus, affords a better picture of the cutting action, and protects the operator from the dangers inherent in any machining process.

Tracer mechanism The tracer mechanism M2 develops, as will become apparent, when off-course or off-line relative to a contour line, error signals that are used in operating the control units 66 and 68. As lbest shown by FIGURE 1 a bracket 16S is suitably mounted both for movement with the tool support 18 and for revolvable movement relative thereto. The disposition of the bracket 16S relative to the optical tower 146 permits a photosensitive device denoted generally at 17u to be located above the screen 152. T he photosensitive device 170 is made up of a photohead 172 that is movable along a drive arm 174 for a reason to be explained. The photohead 172 carries a set 0f on-line or on-course photocells 176, a set of olf-line or off-course photocells 178, and two sets of steering or guidance photocells 18u and 132 all arranged when an on-course path is being `followed as illustrated in FIGURE 4.

The operation of the individual photocells -is wellknown, and, of course, the relationships may be l'altered to lit requirements of different applications. Brie-ily, when a photocell is arranged in series with a voltage source and a load, dark objects cause the photocell to function somewhat as a high resistance; therefore, all of the voltage drop or substantially all of the voltage drop occurs acr-oss the photocell and none happens across the load. With a light object, the resistance of the photocell to current ow is less, and hence, the voltage drop is not as great across the individual photocells.

Since it is desirable to use different size cutting tools and also because cutting tools wear, the movement of the photohead 172 mentioned will compensate for these different size cutting tools. To explain, it must be kept in mind that the contour line 136 appearing on the screen 152 of the tower 146 is considerably magnified, eg., 2G to 1. Therefore, the radius about which the photohead 172 revolves, will have to be a predetermined amount greater than the lactual radius of a circular .cutting tool. For instance, assume that a contour line with the configuration depicted in FIGURE 4d Iis to be cut, Obviously, if the tool radius is greater than the radius of the curve, the line cannot be reproduced unless the tool diameter is reduced to an appropriate size. The same applies to the radius on which the photohead 172 operates, for the photohead radius must be reduced in order to also maneuver around the 20-1 magnified curve. This is done by sliding the photohead 172 lback and forth on the drive arm 174. To obtain accuracy, gauges or the equivalent may be positioned along the drive arm 174 so as to permit very accurate positioning.

Referring to FIGURE 4, which represents the picture seen on the TV viewer 164 when on-line or on-course operation is occurring, the relative positions of the photocells have been shown for explanation purposes only.-

Actually they will not appear on the screen of the TV viewer 16d. The outputs of the various sets of photocells indicate their disposition relative to .the contour line 136, and it is these error signals that `are utilized, as will become evident, for reproducting the contour line 136 on the workpiece 28.

The use of two sets of steering photocells and 182 in maintaining parallel alignment of the photohead 172 with respect to the contour line 136 enhances accuracy since with just one set it can be seen that the contour line 135 may he positioned parallel to the direction of movement of this single set only with respect to the set Whereas other parts of the photohead 172 may be out of parallel alignment therewith, i.e., pursuing a different course. The diagonally opposite Photocells of these steering sets 13) and 182 are so connected that their outputs when a misalignment exists produce a signal of polarity and a magnitude determined by the direction and amount of error. For example, as seen in FIGURE 4a, the bottom or lower photocell 180 of the set 180 and the top photocell 182 of the set 132 may be both positioned over the same line 136. An error signal will be developed such that the photohead 172 assuming O to be the rotational 'axis thereof, will have to be revolved counterf clockwise to attain ,the FIGURE 4 parallel alignment and' Yrihe related set of photocells may be balanced in the saine manner, e'.g.a Wheatstone bridge;

' versed in the art.

negative if the otheris positive, andof a magnitude thatv Y will cause the photohead 172V to be revolved in a clock- Wise direction until the phot-ocel-ls are properly aligned with the contour line 136" as Vin* FIGURE 4.

With theseV two sets of steering photocelis 1S@ and 1S?. arranged to havethe outputs ofk the diagonally opposite photocells joined together, no error signal will be developed as long, as the two sets of photocells 183 and 19,2

are parallel to the contour line 136, but this does notl mean that thephotocells foreach set must straddle the line. placed from the contour line 136 while following a parallel course and vno error signal'will be developed. Be-I cause of this, the on-line set of photocells 176 is incorporated in the photosensitive device 171i for maintaining the tool 26 normal to the contour line 136. These twor on-line photocells 176 if ori-course straddle the contourk line 136 and no error signal is produced, but if thereris a slight lateral deviation, although proper parallel alignment exists relative to the two sets of steering photocells 18) .and 182, an error signal'will be developed of a polarity determined by the side ofthe contour line 135 that the tool 26 has moved off-course, and of a magnitude corresponding to the off-course distance. i

The off-line set of photocells 178 is Yintended to cause n the contrary, they may be considerably dishen, only the one shown in FIGURE 5 will be described; Theothers will' bel exactly thelsame, and the arrangementY be applied :as Vwillf'be understood by those i As seen in FGURE 5, the outputs of the on-linejset of photocells 176 are connected to the input of the preamplifierv 184. ,if bothofthe photocells 176 are positioned over an area formed of material with the same degree of rel'lectively and iprovided with the saineY amount,- of light, the-bridge shouldbe balanced.

Since Vthe outputs generally will not be balanced, then a variable resistor shown at 194 is installed in the.V circuit V,therefor and arranged both in series between a grounded resistor 196 and `a resistor 198 in parallel with a volt- 'age source for the yplriotocells 176. An adjustable, arin for theY variable Vresistor 194 extends to the photocell anodes'bothowhich are joined to the input of the preamplifier '1841, and has a suitable connection with an ammeter 2M orthe equivalentY communicating with the out- Y If the outputs from the put Yof the preampliiierelld. two photocclls are in balance, the needle of the ammeter Zildwill be centered.Y vlf not, a knob 296 may be maneu- Vvered so as to alter thersetting of the adjustable armZiitl and cause the needley to be returned tothe centered position. The variable `resistor 194 therefore functions to establish a reference voltage by causing more or less current ow to ther outputA circuit of the on-line setof photocells 176. f Y

To obtain different polarities, a reference voltage, eg., -85 volts, iis selected for maintaining the needle of the ."ari'irneter 2M centered( Then, if the output is lessy than the apparatus to be stopped whenlthe ,off-course errorV exceeds some predetermined amount. lNormally, as

viewed in FIGUREA and as will be explained, when oncourse the off-line photocells 17% will produce a signal since the outputs therefrom will not be balanced with one of the photocellsY positioned overthe contour line 136.

The error signals from the on-linev` set of photocellsY 176, and the off-line set of photocells 173 Iand the two sets of steering photocells ltl'and 182 are transferred respectively through appropriate preampliers 13d, 135

and 188. The outputs of these preampliiers 15d, 15d and 18S are in turn joined to a brush and slip ring yarrangement displayed at 190 and the various error signals are then picked o'in this manner. amplifiers on the input Vside of theV slip ring arrangement By having the pre- 199, much of the noise from the slip rings is not induced into the control system, and therefore the offers an advantage in this respect. n

The number of photocells in each grouping, -as sets 130, 182, 178 and 176, and their Icapa-city will, of course,fbe determined by the application of the apparatus and accordingly will iniluence the strength of any signals develarrangement oped. With a strong signal, the inuence Von the operation of the tracer mechanism 162 from'external sources,

c.g., intersecting lines, is greatly reduced.

Because there may be different lighting conditions and because the reectively of different masterdrafts, one

may be dark and the other relatively light, yprovisiorri's l made -for balancing the outputs from'the photocells'in eachV of the several sets. This is necessary because Vtvvo otherwise' similar photocells rwill Vgenerally not, under identical conditions, have the saine output and the difference inoutput would produce an error signal in the system. The balancing of the outputs is accomplishedV by a lighting and. reilectively compensator shown generally at 192 in FIGURE 9./

k volts, an error signalV of one polarity Will be produced and if the Verror' signal is greater than the -85 volts, an error signal of an opposite polarity will result. Hcnce,rthe polarity will determine on which side of the contour Vline1`36'the photohead 162 has moved and provide an error ,signal of the proper magnitude and polarity for making the necessary correction.

Asmentioned, theV off-line set of photocells 178 cause operation of the apparatus` to be interrupted if the `offcourse error isftoovgreat. The oit-line error signal developed when the oit-course error has not exceeded the prescribed lim/its Vis'arnpliied by a suitable amplifier 298` and this amplified error signal, as lseen in FIGURE 9, causes a relay 2,1@ to be energized with the result that contacts 2.16ct are normally open and contacts 21d!) are ynormally closed. If the off-course error is too great, then the offline error signal is substantially reduced so that the relay-219 fis deenergized. As a result, contacts Zlila will be closed and'contacts 21% will be opened. Contacts Zliacontrol a circuit for a larrrp 216, which Iwill be stationed on the opera-tors control panel 166 so as to light up when olf-course any prescribed amount. By opening the contacts 2.105, the circuit to the solenoid operated valve 98 will be interrupted kor opened, and hence, the Vsolenoidwinding will be deenergized so as ,to cause the valve '93 tov interrupt the supply of fluid pressure to the motors 54 and 60. Vl`his'stops lautomatic operation until the tool 25 is brought back on course in a Way to be explained.- l

The steering error signals are amplified by a suitable DC. amplifier V21d and then are transferred through a rna'nual-automaticV switching circuit shown at 220 in FIG- URE 9a. In'this switching circuit 22@ a pair of contacts 222@ (seen in FIGURE 6), which are closed during automatic operation by a relay 222 seen in FGURE 8, are closed While related Vcontacts 226e normally closed during manual operation vare opened by a relay 226; Assuming that the various contacts are opened and closed for 'automaticroperatiom the circuit in FIGURE 6, in-

Ymagnetic amplifier 234 is kwell-.known and in this embodiment the magnetic amplifier 234 is joined to a Scott two-phase transformer 236 in such a manner that one phase operates a two-phase motor 23S directly, whereas the other phase is subject to the control of the D. C. steering error signal. The polarity and magnitude of the DC. steering error signal will determine the direction and speed of rotation of the two-phase motor 238.

Associated with the two-phase motor 233 and revolvable thereby is a DC. tachometer generator 240 arranged to produce a feedback voltage corresponding to the speed of rotation of the two-phase motor 238. Also, this feedback voltage may be altered by any suitable adjustment, eg., by variable resistors, in the manner to be explained with respect to the adjustments of the feedback signal voltages supplied the X- and Y- axis summing circuits 112 and 116. This feedback voltage is utilized by the magnetic ampliiier 234 to alter the iniiuence of the error signal-s such that stability of operation results, ie., minor speed iiuctuations do not iniiuence the operation nor does so-called overshooting occur; for otherwise, the twophase motor 233 with a large magnitude error signal Vif not reduced by the feedback voltage would be caused to revolve too fast. If revolving too fast, the motor 233 tends to pass the desired point.

The two-phase automatic guidance or steering motor 23S, as can be observed both in FIGURES 1 and 2, revoiyes a shaft 242 and this shaft in turn causes the drive arm 174 to turn the bracket 168, and accordingly the photohead 172, clockwise or counterclockwise as required and as explained with respect to FIGURE 4a. A speed reducing gear box 244 stati-oued on the output side of the two-phase motor 238 offers a speed reduction determined by the application. On the output side of the gear box 244 a suitable slip clutch 246 is positioned and set to slip at a predetermined torque so las to protect the gear box 244 from damage in case the bracket 168, the photohead 172, or some other part of the drive train offers excessive resistance suiiicient to damage the gear box 244. Next in order, continuing downwardly from the slip clutch 246 and positioned on the shaft 242 are a synchro 248, and two impedances, as automatic steering sine-cosine potentiometer 250 and ori-line sine-cosine potentiometer 252, the functions and purposes of which will be hereinafter explained.

The off-course error signal is amplied by a differential amplifier 254, FIGURE 9, which may be a conventional amplifier with a phase inverter circuit or the equivalent, correlated so that there `are two outputs from the amplitier 254 equal in magnitude but opposite in polarity. The

reason for the duai outputs of opposite polarity can be best i understood by reference t FIGURE 7 and the demonstrated arrangement of the on-line sine-cosine potentiometer 252. As shown, the potentiometer 252 includes a stationary winding 256 connected to the output lines 25S and 260 from the diiierential amplifier 254 and are provided with ground connections at 262 and 264. An X-axis contact arm 266 and a Y-axis contact arm 268, each disposed 90 apart and each revolvable by the lshaft 242, coact with the Winding 256 to produce a control voltage determined by the position of the shaft 242 and the magnitude of the input off-course error signal. The X-axis arm 266 and the Y-axis arm 26S are connected respectively through resistors 270 and 272 and through the manual-automatic switching circuit 220 to the X and Y axis summing circuits 112 and 116. The switching circuit 220 includes automatic and manual X-axis contacts 274a and 274b and automatic and manual Y-axis contacts 274C and 274d, all operated by a relay 274, illustrated in FIG- URE 8.

As can be seen from FIGURE 7, if automatic operation is established, the automatic X and Y axis contacts 274e and 274C are closed while the manual X and Y axis contacts 274b and 2'74d are open. If the reverse is true, ie., manual operation is wanted, the manual X and Y axis contacts 274b and 274d connect the lines extending to the summing circuits to ground and the outputs from the potentiometer 252 do not influence the operation of the X and Y axis summing circuits 112 and 116.

To further understand the operation of the on-line sinecosine potentiometer 252, the position depicted in FIG- URE 7 will first be considered. As can be observed, the X-axis arm 266 is grounded at 262, whereas the Y-axis arm 268 is in contact with the winding 256 at the output line 260. There will be no X-axis signal with this disposition of the potentiometer 252, but there will be a maximum Y -axis signal of a polarity determined by the output line 260. To explain this change of polarity, reference is made again to FIGURE 4d Where the conventional X and Y axes are shown and the contour line is displayed with relation thereto. Assuming initially that the on-line photocells 176 are in the top position so that a negative -output is developed due to the ofi-course error, then if this olf-course error is maintained and the set of photocells 176 continue around the curve in the direction of the arrow, ie., in a counterclockwise direction, the disposition of the photocells 176 relative to the line will be that viewed below the X-axis. Under these conditions the photohead 172 will have been rotated 180. When the photocells 176 were above the X-axis, to correct the off-course error required that the photohead 172 be laterally displaced downwardly in the direction of the arrow and the correction was determined by a negative signal. Now, with the photocell 176 in the position below the X-axis, a correction will have to be made by moving the photohead 172 upwardly in the direction of the arrow if the two photocells 176 are to straddle the line in the on-course position. But, the error signal is still negative and this negative signal causes opposite movement of the photohead 172. However, by revolving the photohead 172 180, the Y-axis arm 268 will contact a point opposite the positive output 253 and the proper correction can be made. Therefore, by having both a positive and negative signal of the same magnitude produced from a single error signal, the proper corrections can be made as the photohead 172 revolves and this situation explained relative to FIGURE 4d `does not present a problem.

So as to aid in understanding the other sne-cosine potentiometers employed in the system as well as the online potentiometer 252, attention is directed to FIGURE 4c Where the arms 266 and 26S have been displaced so that each will have a voltage applied thereto. The Y-axis controlled signal will be positive and the X-axis control signal will be negative in these positions. The magnitudes of each when vectorially correlated on the FIGURE 4b conventional diagram commonly used for solution of circular trigonometric functions will result, e.g., in an angle of 30 as indicated. The resultant of the negative X Value and the positive Y value will require movement equivalent to the value R and in the direction thereot` for the photocells 176 to be positioned straddle the line 136 shown with relation thereto. The resultant R is, of course, the vectorial sum of the X and Y values and it is these X and Y values that cause the drive motors 54 and 60 to be operated so as to result in movement of the tool 26 corresponding in direction and magnitude to the resultant R.

The automatic steering sine-cosine potentiometer 250 functions very similarly to the on-line potentiometer 252 and includes a stationary winding 284, that is joined to input lines 286 and 22S and that has ground connections at 290 and 292. The input lines 236 and 28d provide signal voltages of the denoted polarity but of equal magnitudes corresponding to the desired speed of operation as will become evident. An X-axis contact arm 294 and a Y-axis contact arm 296 are connected respectively through resistors 29S and 300 and through the manualautomatic switching circuit 22th to the X and Y axis summing circuits 112 and 116. As with the on-line potentiometer 252, automatic and manual X-axis contacts 3:02a

13 114. Hence, an amplified regulating signal voltage is afforded for operating tthe control unit 65.

The Y-axis summing circuit 116 and the components thereof have been assigned the same numerals as the X-axis summing circuit 112 but with primes added thereto. For instance, the Y-axis steering control signal voltage input is assigned the numeral Suo', the Y-axis off-course control signal voltage input the numeral 36S', and the Y-axis D.C. tachometer generator the number 378.

The feedback input 37d has installed therein grounded X-axis contacts 394e, whereas the Y-axis feedback signal voltage input 376 has grounded Y-axis contacts 394b. Both of these contacts 39461 and 39411 are operated by a relay 394 in turn under the control of a rapid traverse switch 398 displayed in FIGURE 8 and which may be made accessible to the operator, if desired, by placing within the control panel 166. When this switch 398 is actuated, relay 394 is energized and the contacts 3946: and 394i; are closed, thus shorting the feedback signal voltages to ground and eliminating the influence thereof on the summing circuits 112 and 116. As a consequence, the regulating signal voltage developed will be of a greater magnitude and the motors 54 and 60 will be operated at a faster speed to give rapid movement of the tool 26 at certain times, for instance when it is desired to move the tool 26 quickly to the line to be reproduced.

As will be explained during the operational summary, both manual and automatic operation are possible, therefore, it is necessary to synchronize the rotation of the manual steering shaft 334 with that of the automatic steering shaft 242. There are many ways to accomplish this Aas those versed in the art will understand. However, it is 4slip rings or the equivalent from an external source. The

automatic steering shaft synchro 248 accordingly will function as a receiver and has stator coils 404,'also aligned in a Y, connected to the manual synchro stator coils 402. A rotor winding 406 is revolvable with the automatic steering shaft 242. If preferred, the stator coils may be revolved with the shafts and the rotor windings held stationary.

lf the shaft 242 is out of synchronism with the shaft 334, an A.C. error signal voltage will be developed in the automatic synchro rotor winding 406 indicating the amount that the shaft 242 is out of angular alignment with the shaft 334. To utilize this A C. error signal voltage, it is necessary to develop a DC. equivalent, and hence, rotor winding 4% is joined to a demodulator 40S, which develops from the A.C. error signal voltage a D C. equivalent error signal voltage. This DC. signal voltage is increased to a desired level by an amplifier 419 and if manual operation is effective, this D.C. error signal will be applied to the magnetic amplifier 234 through contacts 226:1 and cause, in the foregoing described manner, the two-phase motor 2318l to be rotated sufficiently to bring the shaft 242 back into synchronism with the manual steering'shaft 334.

If, on the other hand, automatic operation is selected, the contacts 226a will be opened and contacts 226]; closed by relay 226. rThis completes a circuit, similar to that between the amplifier 21S and the magnetic amplifier k234, between the amplifier 410 and a magnetic amplifier 414.

fier 414 in the same way as the magnetic amplifier 234 is controlled, i.e., the magnetic amplier 414 will be connected to the same transformer 236 or a similar one with one phase thereof joined directly to the two-phase motor 346 while the other phase is controlled by this D.C. error signal voltage, such that the two-phase servo motor 346 is caused to revolve the shaft 334 sufficiently to bring the two shafts 242 and 334 into synchronism. The motor 346 and magnetic amplifier 414 also have a D.C. tachometer generator 420 and an adjustment to furnish a feedback voltage for the same reason mentioned with respect to the tachometer generator 244i.

The manual-automatic switching circuit 22% is controlled by a manual-automatic button 422 at the operators control panel 166 and this button 422 operates a manual-automatic switch 424 shown in FIGURE 8. rThe switch 424, when closed, completes a circuit extending from a power supply 426 to relays 274 and 302, 222 and 226. With the switch 424 closed then, automatic operation will take place since all of the associated normally closed contacts are open as contacts 274b, 2'74d, 3ti2b, 302e', and 226g. Those contacts normally open, as contacts 302er, 302C, 274:1, 274e, 22t5b and 222g, will be closed, thus preparing the system for automatic control as will be explained in the operational summary.

Because it may be necessary to maintain the tracing mechanism 162 along a certain course when an intersection between lines is encountered, a freeze button 428 is placed also at the operators control panel 166 for this function and operates a freeze switch 43d illustrated in FIGURE 8. With the freeze switch 43@ in the depicted position, automatic control is possible since the relays 302, 222, and 226 can be energized when the manual-automatic switch 424 is closed. Assuming that the automatic control system is effective, by depressing the freeze button 424, the freeze switch 43) will open and the relays 392, 222 and 226 will return to the position in which the normally closed contacts 302b, 32d and 22er: controlled thereby are again closed as during manual operation. Specifically, the automatic steering control potentiometer 25() is rendered ineffective and the manual steering control potentiometer 340 effective when contacts 3ti2a, 362C are opened and contacts 30245, SttZd are closed. The automatic ori-line signal potentiometer 252 maintains its status, the relay 274 continuing to hold contacts 274s: and 2741: closed, and the contacts 226:1 set-up the described manual-automatic synchronizing between shaft 334 and 242. This part of the operation wiil be further explained during the operational summary.

Chip removal system During the cutting operation it is desirable to withdraw the chips removed from the cutting area as quickly as possible. In this way, the overall effectiveness is enhanced since the removed chips are not permitted to interfere with observation of the cutting action or the workpiece surface smoothness and accuracy and additionally the potential safety hazard from chips is eliminated. The chip removal is achieved by a pressure system demonstrated in FIGURE l0 and the removed chips are transferred to a remote storage place. As illustrated, the spindle 24 to which the cutting tool .26 is attached, is surrounded by a housing 432 so shaped that an annular chamber 434 is formed between the spindle 24 and the housing 432. This annualar chamber is joined to a chip removal tube 436 that communicates with a vacuum pump 438. Chips withdrawn then are transferred by the vacuum pump 433 to a storage bin 444) at some position away from the apparatus. With this apparatus, when machining the workpiece 28 with a helical fluted circular cutter, the workpiece 23 is held against the housing 432 and this feature not only aids in the quick withdrawal of the chips through the fiutes of the cutting tool but also helps maintain the workpiece rigidly supported as will be further explained. Not only are the chips aisee-ie lei moves with the tool 26 and heneewill be Vtracing in an area of the draft table-132 that will 'coinciden/ith the corresponding section of the workpiece 28.

l2. As viewed in FIGURE ll the frame 442 has upper and lower horizontal guideways 444 and 446 and leftand The workpiece support denoted generally at 441 effects this 'and Includes a frame 442 displayedin FIGURES 11 and Vholderbe furnished for the workpiece 28 such that the Y workpiece 2S Vmay be also placed ina corresponding part of the holder. This is because the tracing mechanism` `the locked or clamping position.

downwardly, as viewed in FIGURE 13a, to *soY maneuver VVthe rod 502 that the Vclampraction at bothends relative to the guideways is relieved. When the `handle 4M is' moved to the illustrated position, theV shoe portions 56S Vand S14 will assume ythe illustrated clamping positions.

Preferably, the horizontal guidewayclamp 492 is arranged so Vthat the crank part 49S is overcenter relative to the line of movement'for rod 502 when'the handle 494 is in This renders the clamp 492 self-locking and enables the clamps Vto be maintained n when the handle 49.4 -is released.

right vertical guideways 443 and 450, all of proper `cona,

struction, eg., formed as the tubular guideways illustratved in FIGURE l2. The left and right vertical guideways 448 and 45@ aord guide tracks both for an upper horizontal column 452 that Yhas' left and right end guide sleeves 454 and 45dembracing the vertical guideways wise provided with left and rightend guide sleeves 460 and 462 slidably disposed Ion the left'and right vertical guidways 44S and 4%. The horizontal guideways 444 and 446support both a left vertical column 464 through upperand lower end guidesleeves 46e and 46S and a right vertical column 47d through upper and lower end guide Ysleeves 472 and 474.

' T he opposite ends of each of the horizontal columns '4:2 and 453 are fixed withrespect to their respective guideways by vertical guideway clamps 476. One such clamp is depicted in FIGURES 14 and l5 and employs pivoted atV 482 to the sleeve 452. The lever 486 is actuated by a cam surface 484 on a handle 486 pivoted at 483011 a stud 499 xed to the sleeve462f Consequently, as the `handle '426 is pivoted, the lever 489 is maneuvered lso that the wedge 473 is moved into and out of wedging The mode of clampingA or aftixing one column with respectto the Vother column is demonstrated in FIGURES 16 and 17. Both of the vertical columns 464 and 479 are provided with'V-shaped ways 516 extending the length thereof, whereas both horizontal colums 452 and 458 are formed with .ll/shaped ways 518. Additionally,

i the V-shaped Ways 513 are formed with a' Tslot S26.

V448 and 45t) and a lower horizontal column 458 Vlike-k 1 fr-S101; 520 (see FIGUREN).

:ing action, takes placesecuring the intersecting columns engagement with the guideway 450. The configuration of the cam surface 484' is formed so as to be self-locking, i.e., when the handle 486 is in the locked position 'and is relieved of manual restraint, thus the cam 'surface 434 will maintain the wedgeY 478 in engagement with guideway d. As now can be seen, in the locked position of the handle 485, a clampY action on the guideway 450 occurs between the wedge 47S and thersleeve 462,

the action being in effect similar to that of a vise;

Referring to FIGURES. llV and -13 and 13a, a hori- These ways 51e and SIS and T-slot 52) coact with a double clamp 522 afforded at each intersection of a horizontal column with'a Vertical column and thereby securely maintain the relative positions of each set of intersecting columns. The double clamp 522 has a rotatably movable handle 524 formed'with' a screw portion 526 that is inthreaded engagement with a wedge block 528 engaging one sdeof the V-shapedway 516,. l Between the handle 524 and the opposite side of the V-shaped way die, a slidable wedge block 5,30 is positioned and appropriately guided with respect to the threaded wedge block 523, such ythat when the handley 524 is revolved, vthe threaded connection will cause the two wedge blocks 52.8 and 53) to move into'tight engagement with the sides of the V- shaped way Sie'. LIn doing this, the wedge blocks 526 and 530 climb the sides ofthe Vway 516, and this in turn n causes a T portion 532 ofthewedge blocks .52.8 and 530 to bemoved -into .snugfengagement with the sides of the Hence, a double clamptogether simply yby maneuveringl a single handle. A

spring biased detent533holds the handle524 in the unlocked position'shown by the dotted line in FIGURE 17 spectively inFIGURES 13a andz14.l As displayed in lFIGURE 13a, the horizontalworkpiece holder 534 is tted onto the ways SIS of tht-horizontal column 458 for slidablev movementrand is clamped in Vplace through the action of -a T-bolt 536 threadly engaged with a handle 533. When the handle is turned, ythe T-bolt will snugly `engage the T-slot 52d inthe manner previously described.

zontal guideway clamp 492 is employed to lock the right vertical column 47@ to both the upper and lower horizontal guideways 444 and 446. Clamp 492 includes 'a handle 494 that is pivoted M496 to the column 474) and that has an otlsct crank partiSS with acenter at 5IN).

This oset crank part is Vsuitaoly'attached to arrod 562 L.:

extending the length of the column 470. At the uppery end,the rod 502 is attached to an upper L-shaped'lever At the upper part ofthe horizontalworkpiece holder 534, an abutmentr 544) is formed against whichthe workpiece Z8V is placed, and a clamp screw542 is then ,turned 28 ris, in tight engagement lwith the holders535.. These vertical workpiece holders 535, of course, my beV identical with those used for the horizontal .part of the workpiece if a T-slotis also providedin the 534 pivoted to the end guide sleeve 472 at 506. VLever y 5134 is provided Vwith a shoe portion 5% such'that when the lever 504 is revolved clockwise, as viewedin FIGURE l:

13, the shoe portionv 5% willbe forced into engagement with the upper horizontalv guidewayA 444. Similarly to Yclamps 476 the, sleeve 472 and the shoe portion 568 will,VK dueto the clampingaction, maintain thevertical column 47? stationary at the upper end relative to-the vhorizontal guideway 444. In the same way, the rod 502isfpivotally attachedY at the lower end to a lower L-shaped'lever 5I@ pivoted atr5il2 tothe end guide sleeve 474 and formed lways f 516. y wedge blocks 546 and548 mayg-be made adjustable both,y

relative toreach other and the Ways 516. This enables ,65V

In the absence of a Tslot, two coacting Vthe block S48, for-example, to be loosened and tightened Yfor unclamping and clamping. `vAs with the horizontal workpiecev holders 534,'. thegvertical workpiece holders f 535 also have an abutmentA as'that yat 550 coacting with f a clamp's'crew 552. Y

The movement ofthe horizontalc'olumns 452y and 458 up'and downris rfacilitated-by ra Ycounterweight arrangement shown in FIGURE 11. As there viewed, the upper part of the frame 442 on the left and right sides thereof of the lower horizontal column 458 and the opposite ends extending around the double pulley sets 554 and 556 and attached to counterweights 560. Similarly, cables 562 are attached at opposite ends to the upper horizontal column 452 and counberweights 564 and extend around double pulley sets 554 and 556. The weights of the counterweights are selected so that the horizontal columns 452 and 458 are easily maneuvered, particularly upwardly and so that the clort required to overcome the weights in moving the horizontal columns 452 and 458 downwardly is not excessive.

When moving the horizontal columns 452 and 453 up and down, it is necessary that parallel alignment thereof be maintained, and also that each end of the horizontal columns 452 and 458 be normal to the adjacent guideway. Otherwise, when maneuvering either of the horizontal columns 452 or 458 up and down, tilting could occur and this makes it not only dicult to move the horizontal columns but also induces inaccuracies into the support alignment. For this purpose, an aligning arrangement is provided comprising a double pulley S66 (see FIGURE 13) revolvably supported at each end of the horizontal columns 452 and 458. These pulleys 566 coact through wires to maintain the desired alignment.

To understand this more clearly, reference is made to FIGURE 11 and as shown, a wire 568 is attached at one end to the lower right part of the frame 442 at 570 and extends around the pulleys 566 at each end of the lower horizontal column 458, and then upwardly to a point on the frame 442 in the vicinity of the left end of the upper horizontal column 452 where the opposite end of the cable 56S is attached at 572. A second wire 574 has one end attached at 576 to the frame 442, this point being near the left end of the lower horizontal column 458, is wound around each of the pulleys 566 at the opposite ends of the horizontal column 458, and then extends upwardly where it is attached at point 578 to the upper horizontal column 452. A third wire 580 starts at the point 582 at the upper left part of the frame 442, extends around the pulleys 566 on each end of the upper horizontal column 452 and is attached at 584 to the lower right part of the lower horizontal column 458. The fourth wire denoted by the numeral 586 starts at 587, extends around the pulleys 566 on each end of the upper horizontal column 452 and ends at point 588 on the lower horizontal column. With this system of wires and pulleys, as the horizontal columns 452 and 458 are maneuvered, each end thereof is maintained in strict alignment so that there is no tilting or cocking permitted.

Another aspect of this workpiece support 4431 is the relationship of the cutting tool 26 to the workpiece 28. The cutting tool 26 preferably has helical flutes thereon and, as mentioned before, this aids in causing the chips to be withdrawn along the spindle 24 by the vacuum system, and also contributes to the maintenance of the engagement between the housing 432 and the workpiece 28. This engagement eliminates the need for rigid support of the workpiece 28 on the side opposite the tool 26.

To aid in accurately positioning the workpiece, graduated scales 589 and 598 are provided in vertical and horizontal directions as viewed in FIGURE 1l and are atiixed to the frame 442 so as to be adjacent pointers 592 and 594 movable with the columns.

The described workpiece support 441 by the system of moving the horizontal and vertical columns permits a workpiec-e 28 to be placed anywhere within the areas defined by these columns; in other words, the workpiece 28 may be placed in a lower right corner of the frame 442, in the middle of the area provided therefor, or at any other part thereof.

Before either operation can be commenced, there are certain adjustments. For instance, the proper size cutyting tool 25 must be installed, for this size will determine the position of the photohead 172 on the arm E74 in relation to the axis of rotation of the motor 238. Also,

the proper size reticle 156 must be selected to correspond to the tool size. After the master draft 134 is attached to the draft table 132 and the required power turned on, the next step requires the balancing of the outputs from the dilerent sets of photocells in the previously described manner, i.e., by adjusting knob 286 so as to center the needle of ammeter 264.

OPERATIONAL SUMMARY As has been previously mentioned several times, there are two aspects to the control of the reproducing apparatus. One offers manual control, which is possible through a manual control system, and the other is automatically achieved through the automatic control system.

Manual control Manual control requires that the manual-automatic switch 424 be open, and as a result, contacts 3tl2b, 302d 274er, 274e' and 226er will be closed and cause the associated circuitry to be effective. Also, preferably the offcourse error signal voltage and its influence on relay 210 is eliminated during manual control so that the Solenoid operated valve 98 will not be held closed, especially when the photohead i172 is a substantial distance ofi-course. For this purpose, a switch (not shown) or the equivalent, may he installed between the preamplifier 186 and the amplifier 258. Before any movement of the cutting tool 25 relative to the workpiece 28 can take place, the speed control dial 312 must be maneuvered towards the On position so as to cause limit switch control 338 to render the solenoid operated valve 98 ineffective to block pressure tiuid from the control units 65 and 68. The corresponding speed control signals developed by the speed control potentiometers 318 and 320 will be supplied to both the automatic and manual steering control potentiometers 340 and 254i, the manual steering potentiometer 34@ only being effective. By now maneuvering the steering control dial 332, and while viewing the relative positions of the simulated cutter image and the image of the contour line 136 on the TV viewer 164, appropriate X-axis and Y-axis control signal voltages can be developed by the manual steering potentiometer 340 and applied to the X and Y- axis summing circuits 112 and 116. It should be kept in mind that these X-axis and Y-axis control signal voltages also include the desired speed signal. These control signal voltages then are summed along with the oscillating and feedback signal voltages and corresponding summe-:i regulating voltages determined by the gain potentiometers 392 and 392 are applied to the amplifiers 1114 and M8. These amplified regulating voltages are delivered to the control units 66 and 68 whereupon the drive motors 54 and 60 cause movement respectively of the table i2 and the tool support 18 such that the cutting tool 25 is moved along a desired path, the resultant of the table and tool support movements. This desired path will, of course, coincide with the contour line 136 on the master draft 134 if tracing manually. Additionally, if the rapid traverse switch 398 is closed, the elimination of the feedback will permit the tool 26 to be maneuvered at a faster speed as has been indicated.

During manual operation the tracer mechanism 162 serves no function; however, the automatic steering shaft 242 is maintained synchronized with the manual steering shaft 334 so that at any time automatic control can be initiated without any lag or lost motion therebetween.

Automatic control Before automatic contr-ol is initiated, it is assumed that the adjustments mentioned in the description of the manual control have been made, i.e., the outputs of the different sets of photocells are balanced, the photohead 272 is adjusted so as to correspond to the size of the cutting tool 26, the master draft 134 is in place, and the workpiece 28 has been installed to the workpiece support 441. The tracing mechanism 262 can now be moved man-

Claims (1)

1. IN APPARATUS FOR REPRODUCING A CONTOUR FROM A PATTERN, THE COMBINATION OF A COPYING TOOL, A TRACER MECHANISM INCLUDING MEANS SENSING THE PROXIMITY OF THE TRACER MECHANISM TO THE CONTOUR AND DEVELOPIGN A CORRESPONDING OUTPUT FOR CAUSIGN THE COPYING TOOL TO BE MANEUVERED SO AS TO REPRODUCE A CONTOUR ON A WORKPIECE, AN ELEMENT SIMULATING THE CONFIGURATION OF THE COPYING TOOL, THE ELEMENT BEING ARRANGED REMOTELY OF THE COPYING TOOL AND ALSO MANEUVERABLE BY THE TRACER MECHANISM SO AS TO HAVE MOVEMENTS CORRESPONDING TO THE MOVEMENTS OF THE COPYING TOOL, IMAGE PRODUCING MEANS, AN OPTICAL SYSTEM COACTING BOTH WITH THE ELEMENT AND THE IMAGE PRODUCING MEANS SO AS TO PROVIDE THE IMAGE PRODUCING MEANS WITH

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